1. Field of the Invention
The present invention relates to a method and a system for manufacturing organopolysiloxane. Particularly, the method is achieved by a quasi-continuous way through cascade equipments coordinate with automatic control. By prior established performance empirical relationship between the raw materials and the products, the computer automatic control is used to manufacture the organopolysiloxane with different viscosities and different end functional groups. The quasi-continuous processing of the invention combines with batch chemical reaction conditions, chemical equipment disposition, process control and so on to achieve the purpose of massive and flexible manufacturing of different organopolysiloxanes.
2. Description of the Prior Art
Polysiloxane is the main basic chemical structure unit of silicone fluid and silicone rubber, and the derivatives thereof can be used to make products widely applied in the national defense and different industries.
In prior art, alkali or acid catalyst is used for cyclic polysiloxane monomer to carry on a ring-opening polymerization reaction, so as to manufacture certain linear high-viscosity silicone fluids and major parts of silicone gums. The cyclic polysiloxane monomer can be represented as (R1R2SiO)n, wherein R1 and R2 are univalent hydrocarbon groups with carbon numbers from 1 to 12, while n is a positive integer from 3 to 8. Particularly, D4 (octamethylcyclotetrasiloxane) (n=4) is one of the most popular cyclic polysiloxane monomer.
The aforementioned polymerization reaction usually uses the dosage of mono-functionality end-blocker, or chain stopper (M2), or the proportion of M2 and D4 to control the viscosity and the end functional group of the organopolysiloxane of the product, then the steps of eliminating catalyst and devolatilization are applied to provide polymeric product for downstream formulation applications.
In the polymerization reaction application, if the product is applied with high temperature, strong inorganic catalyst carried therein is not easy to be neutralized completely, a tiny amount of catalyst may still remain in the product, so that the stability under high temperature of the product is therefore deteriorated. Accordingly, in general, strong inorganic catalysts will not be used for high temperature applications.
Although the above-mentioned processes may differ, batch process is usually taken in the laboratory scale. Furthermore, some industrial operating processes may retain batch-wise when scale up.
According to the report of Stanford Research Institute (Scheeline, H. W and Chandwani, D. Silicones, A private report by Process Economics Program, Report no. 160, Menlo Park, Calif., p. 142-150, p. 194-195, p. 281-285, 1983), the difficulty of above-mentioned product industrialization with batch process manufacturing includes: uneven high viscosity mixing which may cause uneven product, and the difficulty of removing catalyst may cause the product to be inactive in high temperature application. Therefore, transient catalyst, which is decomposable in high temperature, such as TBPH (tetrabutylphosphonium hydroxide) or TMAH (tetramethylammonium hydroxide), is suggested to catalyze the polymerization reaction. The way of said process is to carry on the polymerization reaction by the heat exchanger type polymerizer of high length-to-diameter ratio, while the batch reaction time is substituted by the average retention time of continuous reaction in exchanger type polymerizer, and then the raw product is subjected to devolatilization process and so on. Besides Stanford Research Institute promotes the continuous type process, there are many documents with the design of continuous type process in the prior art, whose differences are concentrated in the processing equipment, and discussion of unnecessary details will be hereby omitted.
Development of any chemical synthesis product may start with batch operation during the initial research period. Depends on market demand and degree of the process's complexity, either batch-type design or continuous-type design may be chosen for scale up operation. Traditionally, batch-type scale up is easier and relatively cheaper, especially for the production of organopolysiloxane. Because the polymerization reaction of organopolysiloxane has the characteristics of insignificant exothermic heat of reaction and long reaction time, it is even easier to use the batch-type scale up directly. However its shortcoming is small yield and high manpower for specific yield.
Yet it is not straightforward to design continuous-type reactor by using batch laboratory reaction data. The traditional rule is to obtain the chemical kinetic models (the empirical model or the mechanistic model) first, and then bring mass balance model and flow field model of different-type continuous reactors to carry on a series of study routes, such as simulation yield calculation, bench scale and pilot scale facilities erection and testing, software and hardware revision, etc. to verify the accuracy of the design, and finally build a full chemical plant, and after successful test runs to obtain products of mass manufacture continuously. This scale up strategy must invest many research and development resources in the design stage, especially needs to purchase many control instruments to maintain continuous operation. The investment expenditure is much higher than the one of the batch process. In addition, the continuous-type process will cause the loss of the raw material during process shutdown or startup. Moreover, the continuous-type process lacks manufacturing flexibility in accordance to moderate demand for each different specification products, and therefore is not favorable for the manufacture and sale strategy of the small to medium enterprises.